The \(\beta \) -like event selection in Borexino for neutrino candidate identification is described in details in [1]}: the basic idea is to select point-like events in the innermost part of the Inner Vessel, avoiding cosmogenic background induced by muons crossing the scintillator and limiting the internal contamination from radioactive decays.
It is worth mentioning that the evidence of the annual modulation of the solar neutrino flux due to the Earth's orbit eccentricity in Borexino was already reported in Phase-I (3 years, \(\approx 3\sigma \)  level [1]}) and the first part of Phase-II (5 years, \(3.5 \sigma \)  level [3]}). The previous analysis was performed using the Lomb-Scargle method [4]}, [5]}, the Empirical Mode Decomposition approach [6]}, and the standard least square sinusoidal fit.
